#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int jiecheng(int n)
{
	int sum = 1;
	for (int i = 1; i <= n; i++)
	{
		sum *= i;
	}
	return sum;
}
int main()
{
	int n;
	scanf("%d", &n);
	int sum = 0;
	int ret=1;
	for (int i = 1; i <= n; i++)
	{
		ret *= i;
		sum+=ret;
	}
	printf("%d", sum);
}

//int main()
//{
//
//}